1. Field of the Invention
The present invention relates to a content storage system that encodes content such as video signals and audio signals to be used in, for example, broadcasting stations to broadcast programs, and stores this content in a plurality of storage apparatuses, a storage apparatus for use in the system, and a method of controlling the storage of content.
2. Description of the Related Art
The broadcast-program on-air system used in any broadcasting station has video servers (storage apparatuses). Each video server encodes and stores content, such as video signals and audio signals to be used in the programs. In response to an on-air request for a program, the video server decodes the content. The content decoded is read from the video server and transmitted. To respond the on-air request reliably, two video servers, i.e., an acting video server and a reserve video server, are operated in parallel. If any trouble develops in the acting video server, the output is instantly switched from the output of the acting video server to the output of the reserve video server. In some cases, another reserve video server may be used, whereby three video servers operate are operated at the same time.
The video servers used in the broadcast-program on-air system described above are operated in parallel receives the same content, encode the content and store the content encoded, in order to transmit the same stored content in accordance with the schedule of broadcasting programs. Two methods are available for storing the same content into a plurality of video servers. In one method, the same content is input to the video servers at the same time, or in parallel. In the other method, the video servers are connected to the source of the content, one after another, so that the content may be stored in one server at a time.
In order to copy the data files of content, such as video data, in a plurality of storage apparatuses such as video servers, a plurality of playback heads may read the same content from a recording medium and the content thus read may be stored in the storage apparatuses (e.g., video severs) at the same time. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 5-210909, page 5 and FIG. 1.)
Any video server used in the broadcasting station should be so designed that no video data containing noise resulting from errors made during the storage is broadcast and played back. In many cases, the video and audio signals stored in the video servers are data, such as Moving Picture Experts Group (MPEG) data, which have been compressed and encoded to content data for broadcasting. If the compressed and encoded data stored in the video servers contains an error, which may be only a one-bit error, the decoding of the compressed codes will be much influenced, greatly impairing the quality of image played back.
With a data storage apparatus of the ordinary type, it suffices to compare the digital data input to it with the digital data output from it, thereby to confirm that the input data and the output data are identical to each other. In any video server used in the broadcasting station, however, the process of storing data involves the above-mentioned conceding. Therefore, not only the stored data, but also the data encoded and the data decoded must be checked and confirmed. In other words, all signals decoded in each video server, which will be broadcast, should be monitored to determine whether they can be converted to images and sounds similar to the original images and sound.
Thus, the data stored in each video server is previewed to see whether the data has no errors, or whether the data has quality high enough to be broadcast. The greater the number of video servers used, which operates in parallel with the acting video server, the longer the time that must be spent in previewing the data in the video servers, as long as the data (i.e., content) remains stored in all video servers. In addition, the working load on the operators who preview the video servers will inevitably increase.
As described above, with the content storage system used in, for example, any broadcasting station, the data accumulated in the storage apparatuses operating in parallel must be previewed again and again as long as the data remains stored in the storage apparatuses. Much time is required to preview the content in the storage apparatuses, and the working load is large on the part of the operators who preview the data.